A Global Warming Flap

Published: 06/29/2010

Florian Altermatt likes to chase butterflies, but he’s also a scientist who thinks that butterflies might have something to tell us about the effects of global warming.

Altermatt is an ecologist — a scientist who studies how creatures interact with their environment — who works at the University of California, Davis. In a new study, he and other researchers looked at changes in the reproduction patterns of butterflies and moths in Central Europe.

Over the last 30 years, the average temperature in Central Europe has gone up about 1.5 degrees Celsius. During that same time, 44 species of moths and butterflies in an area around Basel, Switzerland, have added an extra generation to their numbers during some years, Altermatt found. That means that if butterflies of one of these species used to reproduce once per year, they now sometimes reproduce twice. And if they used to reproduce twice, they now sometimes reproduce three times. These extra generations didn’t show up in this location before 1980.

The temperature increase, 1.5 degrees, may not seem like much, but it’s about the difference between the body temperature of a healthy person and someone with a low-grade fever. Altermatt suspects that in Central Europe, that extra degree and a half is changing the internal clocks of many kinds of butterflies and moths. Because it’s warmer outside, their breeding season begins earlier, for example, giving the insects more time to mate. Altermatt also says that the increase in temperature speeds up the development of the insects, so they’re ready to reproduce earlier in their lives.

This was no small study: He and his colleagues watched butterflies and moths outdoors and also looked at historical records for more than 1,100 types of the creatures. Of those species, 263 are known to produce one or two extra generations in the location studied — but not always; only when the temperatures heat up. Altermatt found, however, that since 1980, a majority of those species started adding generations more often.

These added insects might mix things up in the ecosystem of Central Europe, says Patrick Tobin, an ecologist who works for the U.S. Forest Service in Morgantown, W.Va. An extra generation of insects provides more food to the animals that feed on them. Those predators, in turn, might start to increase their numbers, which would make life tougher on the other species the predators eat, Tobin told Science News. On the other hand, with an extra generation, an endangered insect species might have a better chance of recovering.

Altermatt also does research in evolution, which is the study of how species, or groups of the same creature, change over time. Every time an insect — or animal, plant or other organism — reproduces, the offspring might be slightly different from its parent. These differences could give the offspring a better chance of survival in the world. In this case, Altermatt thinks the additional butterfly generations may speed up evolution — and perhaps give them a better chance of survival in the face of climate change. On the other hand, maybe these changes won’t make a difference: Altermatt doesn’t know whether the extra generations of butterflies and moths survived.

Scientists who study the effects of climate change like to look at patterns such as insect populations because they are easy to track — and easy to connect to a warming world. And by studying such visible effects of climate change, scientists might be able to better predict the changes ahead for other populations — like humans.